The current standard communications design in a railway vehicle comprises a CAN bus which enables data to be communicated along the train between devices including the brake control units.
The CAN communication protocols have proven themselves over several decades of use. It is now conventional to use standard laptop computers to operate diagnostic software and the like, which laptops can be plugged into the CAN bus and be used to communicate with the brake control units. The standard interfaces currently used in Train Management Systems (TMS) such as RS-485, MVB and FIP are regarded as being too slow by users, who want to use faster standards such as Ethernet.
Ethernet in this context describes the lower-level communications system i.e. the physical layer and simplest data packet transfer. Users require higher-level protocols to be supported that sit on top of Ethernet e.g. Profinet, CIP, TCP, UDP, Web server, maintenance.
As brake systems are safety critical, it is necessary that any executable software code that runs on the brake control unit and any modules associated with the brake control unit such as wheel slide protection is tested and validated to SIL2 (Safety Integrity Level 2). The problem that this causes is that each new module fitted to the system would need to be validated to SIL2. However, this requires several man years' work and is too expensive and time consuming for most projects.
GB 2395241 discloses a trailer brake electronic control unit. The ECU has non volatile storage memory means for storing braking related control parameters particular to the vehicle and discretely programmable storage means to carry operating data for one or more auxiliary functions of the vehicle. This is operable to check one or more incoming and outgoing variables and control algorithms against a predefined list such as to safeguard the braking function against error modes. This approach suffers from the drawback that it does not meet users' requirements for new APIs (application programming interface) to support new protocols and interface cards as the functionality in the control unit is limited.
The present disclosure provides a more flexible brake control unit arrangement.